A photovoltaic cell (e.g. a solar cell) usually includes a substrate having a front side and a rear side. Conventionally, a contact structure is provided on at least one of the both sides. Typically, the contact structure has a width of at least about 100 μm and a thickness in the range of only about 10 μm to about 15 μm. An increased width of the contact structure may result in a decrease of the efficiency due to the increased shadowing caused by this. Furthermore, a reduction of the width of the contact structure may result in an increased line resistance of the contact structure. Moreover, the electric current provided by the individual contact structures is usually collected by means of so-called busbars, which may cause additional shadowing of e.g. the front side surface of the substrate.
The electric connecting of photovoltaic cells is usually carried out by means of contact bands, which are soldered onto the busbars of the photovoltaic cell. In this case, the entire current is guided through the contact bands. In order to keep the resistance losses as low as possible, the contact bands require a certain total cross section area. This results in an increased shadowing of e.g. the front side surface of the substrate.
In order to achieve an improved photovoltaic module (e.g. solar module), the contact structure of the photovoltaic cell and the number and dimension of the contact bands may be combinatorial optimized.
In this case, it has been found out that a high number n (n usually greater than 30) of thin (e.g. having a diameter of less than 250 μm) electrically conductive wires may be useful. Furthermore, it is to be expected that due to a punctual fixation of the wires on the photovoltaic cell, less mechanical tensions may be caused due to different thermal expansion coefficients of the wires on the one hand and the photovoltaic cell on the other hand.
In practice, there is a need to easily and efficiently handle and position the thin wires on the photovoltaic cell.
DE 102 39 845 C1 discloses a method for positioning a plurality of wires on a photovoltaic cell, wherein the wires are fixed on an optically transparent film by means of an optically transparent adhesive. Then, the optically transparent film is fixed to the metallization of the solar cell. According to DE 102 39 845 C1, the optically transparent film as well as the optically transparent adhesive remain in the solar module which is formed by serial coupling of a plurality of such solar cells. This results in a rather high demand to the optically transparent film as well as the optically transparent adhesive with respect to their long-term stability. This causes rather high costs.